Chromosomal Chromosomal DisordersDisorders

What are chromosomes?What are chromosomes?

Humans have 23 Humans have 23 pairs of pairs of chromosomes, with chromosomes, with one chromosome one chromosome from each parent. from each parent. The chromosomes The chromosomes are coiled up DNA. are coiled up DNA. Under normal Under normal conditions all of the conditions all of the chromosomes are chromosomes are inherited in tact. inherited in tact.

This is a normal karyotype of

human chromosomes. A karyotype is a picture of chromosomes lined up to look

at and compare.

Chromosomal DisordersChromosomal Disorders Chromosomal deletionChromosomal deletion: when cells go through : when cells go through

meiosis, portions of the chromosome are lost.meiosis, portions of the chromosome are lost. Chromosomal inversionChromosomal inversion: when cells go : when cells go

through meiosis, parts of the chromosome through meiosis, parts of the chromosome are flipped.are flipped.

Chromosomal translocationChromosomal translocation: when cells go : when cells go through meiosis, parts of the chromosomes through meiosis, parts of the chromosomes stick together and switch.stick together and switch.

Chromosomal non-disjunctionChromosomal non-disjunction: when cells go : when cells go through meiosis the chromosomes don’t through meiosis the chromosomes don’t separate correctly and either too many or not separate correctly and either too many or not enough are passed on.enough are passed on.

Single Chromosome DisordersSingle Chromosome Disorders

1.Deletion

• Genetic material is missing

2. Duplication

• Genetic material is present twice

3. Inversion

• Genetic material is “flipped”

Two Chromosome DisordersTwo Chromosome Disorders((Both types are called “translocation”)Both types are called “translocation”)

Insertion

• Genetic material is added from another chromosome

Translocation

• Material is swapped with another chromosome

Turners SyndromeTurners Syndrome1 in 5,000 births

45 chromosomes X only

#23 MonosomyNondisjunction

96-98% do not survive to birthNo menstruationNo breast developmentNarrow hipsBroad shoulders and neck

Cri-Du-Chat SyndromeCri-Du-Chat Syndrome 1 in 216,000 births

46 chromosomes

#5 Deletion of lower arm

Symptoms:

Moon-shaped

face

Heart disease

Mentally

retarded

Malformed

larynx

Normal lifespan

Aniridia-Wilms Tumor Aniridia-Wilms Tumor SyndromeSyndrome

1 in 50,000,000 births

46 chromosomes

XY or XX

#11 Deletion of upper

arm

Symptoms:

Mentally retarded

Growth retarded

Blindness

Tumors on kidneys

Short lifespan

Thirteen Q Deletion SyndromeThirteen Q Deletion Syndrome

1 in 500,000 births

46 chromosomes

XY or XX

#13 Deletion of lower arm

Mentally retardedDeformed faceNo thumbsHeart diseaseShort lifespan

Prader-Willi SyndromePrader-Willi Syndrome1 in 5,000,000 births

46 chromosomesXY=97% XX=3%

#15 Deletion of lower arm

Small bird-like head

Mentally retarded

Respiratory problems

Obesity

Short lifespan

Eighteen Q Deletion SyndromeEighteen Q Deletion Syndrome

1 in 10,000,000 births

46 chromosomes

XY or XX

#18 Deletion of lower arm

Mentally retardedHeart diseaseAbnormal hands and feetLarge eyesLarge earsNormal lifespan

Burkitt LymphomaBurkitt Lymphoma

Translocation of the Myc gene on chromosome 8

Normal Myc genes control cell growth and division

•Translocated Myc genes don’t function properly

•Leads to cancer of the lymph nodes

Down Syndrome: Trisomy

Down Syndrome

1 in 1,250 births

47 chromosomesXY or XX

#21 Trisomy Nondisjunction

1 in 31,000 births

46 chromosomesXY=97%

XX=3%

#14/21 Translocation

Down SyndromeDown SyndromeShort, broad hands Stubby fingersRough skinImpotency in malesMentally retardedSmall round faceProtruding tongueShort lifespan

Klinefelter SyndromeKlinefelter Syndrome1 in 1,100 births

47 chromosomesXXY only

#23 Trisomy Nondisjunction

Scarce beard

Longer fingers and arms

Sterile

Delicate skin

Low mental ability

Normal lifespan

Other Types of Inherited Other Types of Inherited Genetic Disorder…Genetic Disorder…

Tay-SachsTay-Sachs

Multiple kinds of mutation on Chromosome 15

Tay-SachsTay-Sachs incidence rate of incidence rate of

infantile Tay-Sachs= infantile Tay-Sachs= • Ashkenazi Jewish Ashkenazi Jewish

groups, French groups, French Canadian & Cajun: Canadian & Cajun: 1 in 30 are carriers1 in 30 are carriers

• other groups: 1 in other groups: 1 in 300 are carriers300 are carriers

accumulation of lipids on accumulation of lipids on brainbrain

brain malfunction; death by brain malfunction; death by age 5age 5

Sex-linked: X chromosomeSex-linked: X chromosome Duchenne Muscular Duchenne Muscular

DystrophyDystrophy 1 boy in every 3,0001 boy in every 3,000 progressive progressive

weakening of weakening of muscles and loss of muscles and loss of coordinationcoordination

more common in more common in malesmales

Cystic FibrosisCystic Fibrosis

1/31 is carrier in U.S.1/31 is carrier in U.S. Single gene mutationSingle gene mutation mucus in lungs, mucus in lungs,

pancreas, digestive pancreas, digestive tract and other organstract and other organs

most common lethal most common lethal genetic disease in genetic disease in U.S.U.S.

heterozygote heterozygote may be may be resistant to resistant to typhoid fevertyphoid fever

Autosomal DominantAutosomal Dominant

Huntington’sHuntington’s incidence: incidence:

1/10,000 in U.S.1/10,000 in U.S. nervous system nervous system

degeneratesdegenerates

late onsetlate onset may not show may not show

symptoms until past symptoms until past reproductive agereproductive age